Stereospecific Synthesis of the Geometrical Isomers of a Natural ProductT. Grove, D. DiLella, and E. VolkerPresents an experiment for the synthesis of (Z) and (E) isomers that is presented to students as a puzzle in which they must determine the identity of the major component in anise oil. A necessary part of the analysis is the preparation the (E) and (Z) isomers of anethole. Molecular modeling is used to explore the conformation of and energy difference between isomers.Grove, T.; DiLella, D.; Volker, E. J. Chem. Educ.2006, 83, 1055.

Alkenes |

Computational Chemistry |

Gas Chromatography |

IR Spectroscopy |

NMR Spectroscopy |

Stereochemistry |

Synthesis

Ozonolysis Problems That Promote Student ReasoningRay A. Gross Jr.The structural features inherent in acyclic monoterpenes that follow the isoprene rule often lead to unique sets of ozonolysis products from which their structures, excluding stereochemistry, can be determined from molecular formulas only. This article shows how students may elucidate the structures of these compounds by analysis of the oxidative and reductive workup products.Gross, Ray A., Jr. J. Chem. Educ.2006, 83, 604.

Cis and Trans Isomers of CycloalkenesSusan E. Barrows and Thomas H. EberleinThe purpose of this article is to provide that analysis. In order for a cycloalkene to accommodate a trans double bond one or more of the following nonideal geometries must occur: a twisted p bond; pyramidal sp2-carbon atoms; nonideal sp3 bond angles; or longer than normal CC single and double bonds. This article provides a list of experimentally determined relative energies of the cis and trans isomers within the series cycloheptenecycloundecene, along with computationally derived energies at several levels of theory. It also examines the geometric distortions through which cycloalkenes relieve the strain introduced by a trans double bond. Barrows, Susan E.; Eberlein, Thomas H. J. Chem. Educ.2005, 82, 1334.

Computational Chemistry |

Molecular Modeling |

Alkenes |

Diastereomers

Understanding Rotation about a C=C Double BondSusan E. Barrows and Thomas H. EberleinWe present a simple method of introducing the concept of a flexible C=C pi bond into beginning organic chemistry courses. We report the energetic demands of partial twisting about the C=C bond in 2-butene as calculated using DFT, LMP2, and MCSCF methods. Finally, using the results of these calculations, we assessed the degree of strain introduced by the twisted nature of the C=C bond in trans cycloalkenes. Barrows, Susan E.; Eberlein, Thomas H. J. Chem. Educ.2005, 82, 1329.

Computational Chemistry |

Molecular Mechanics / Dynamics |

Molecular Modeling |

Alkenes

Cis and Trans Isomerization in Cyclic Alkenes: A Topic for Discovery Using the Results of Molecular ModelingSusan E. Barrows and Thomas H. EberleinThis article describes an activity in which students are led to discover the fundamental reasons behind the unusual instability of the trans isomers in medium-sized cycloalkenes by using the results of molecular modeling. Notably, students will make the unexpected discovery that twisting about p bonds is perhaps more facile than they had been led to believe. Barrows, Susan E.; Eberlein, Thomas H. J. Chem. Educ.2004, 81, 1529.

A History of the Double-Bond RuleBernard E. HoogenboomFrom his experience as an industrial chemist, Otto Schmidt recognized the bond weakening in hydrocarbons and in 1932 postulated the "Double-Bond Rule," stating that the presence of a double bond in a hydrocarbon has an alternating strengthening and weakening effect on single bonds throughout the molecule, diminishing with distance from the double bond.Hoogenboom, Bernard E. J. Chem. Educ.1998, 75, 596.

Learning Theories |

Mechanisms of Reactions |

Alkenes

On the Disproportionations of Cyclohexene and Related CompoundsAlex Bunjes, Ingo Eilks, Manfred Pahlke, and Bernd Ralle*The catalytic hydrogenation of liquid hydrocarbons is easy to realize in a simple laboratory experiment using a palladium catalyst. In the case of hydrogenation cyclohexen or cyclohexadiene in addition to the expected finding of cyclohexane among the hydrogenation products, the formation of benzene can be observed. In absence of hydrogen, the disproportionation of both starting materials to cyclohexane and benzene takes place.Bunjes, Alex; Eilks, Ingo; Pahlke, Manfred; Ralle, Bernd. J. Chem. Educ.1997, 74, 1323.

A Simple and Safe Catalytic Hydrogenation of 4-Vinylbenzoic AcidDe, Shantanu; Gambhir, Geetu; Krishnamurty, H. G.An alternative procedure to catalytic hydrogenation is catalytic transfer hydrogenation. In this technique, the reduction of an organic compound is achieved with the aid of a donor substance in the presence of a catalyst.De, Shantanu; Gambhir, Geetu; Krishnamurty, H. G. J. Chem. Educ.1994, 71, 992.

Catalysis |

Oxidation / Reduction |

Alkanes / Cycloalkanes |

Alkenes |

Alkynes

The electrophilic addition to alkynesWeiss, Hilton M.Electrophilic additions to alkynes traditionally do not receive as much attention in organic textbooks as electrophilic addition to alkenes.Weiss, Hilton M. J. Chem. Educ.1993, 70, 873.

The dehydration of 3,3-dimethyl-2-butanolTaber, Richard L.; Grantham, Gary D.; Champion, William C.Presents an experiment that demonstrates the usefulness of gas chromatography as an analytical technique, emphasizes structural rearrangement, makes use of elementary thermodynamics, and gives the student some experience in the original literature.Taber, Richard L.; Grantham, Gary D.; Champion, William C. J. Chem. Educ.1969, 46, 849.